5.3 Impacts on greenhouse gas emissions
The projected increase in demand for natural gas as a cleaner
energy alternative to coal is one of the main drivers behind global coal seam
The burning of natural gas (largely methane) is generally
viewed as having much lower greenhouse emissions compared to coal (Rutovitz et
According to the APPEA (2012) coals seam gas is a clean
burning fuel producing up to 70% fewer greenhouse gas (GHG) emissions than some
existing coal technology.
Burning methane produces less emissions but when viewing
emissions in terms of the entire life cycle of methane the difference between
CSG and coal may not be as significant as claimed.
An Australia report into the life cycle GHG emissions from
electricity sources revealed that CSG was only marginally better than coal. CSG
was found to be 13-20% more GHG intensive than conventionally produced Liquid
Natural Gas (LNG) and only 5% less than the most efficient coal power.
The more intense extraction process creates the potential for
high emissions throughout the life cycle of CSG production (Hardisty et al,
Methane (CH4), like carbon dioxide (CO2), is a long lasting
greenhouse gas that persists in the atmosphere for a long time and has long term
impacts on climate.
According to science CH4 is 20 times more effective as a GHG
than CO2 a factor which needs to be considered when assessing the life cycle
impacts (IPCC, 2007).
A paper prepared for the National Climate Assessment revealed
that CH4 is the second largest contributor to human caused global warming after
Natural gas systems are the single largest source of methane
emissions in the United States representing almost 40% of the total fluctuation
(Howarth et al, 2012).
It seems that some climate assessments by CSG companies
overlook the potential impacts of fugitive emissions from CH4 production.
Arrow Energy made only one reference to fugitive emissions in
their environmental impacts statement (EIS) by “preventing flaring and venting
as far as practicable” (Arrow Energy, 2012, pp. 22) at gas wells and did not
mention methane leaks or include impacts from transport or production of GTL or
leakages from well heads (Arrow Energy, 2012).
QGC (2012) acknowledges fugitive emissions as a possible
emission source and in their EIS notes that the highest methane emissions source
comes from pipeline leakages at 8.7kg/diesel equivalent CO2.
However, the time scales for these emissions were not included
and nor were well head fugitive emissions. Gas wells have been reported leaking
in Queensland by local surveys and government safety assessments.
Out of 58 wells tested in Tara, QLD a total of 26 were
reported leaking, 5 of which were reported above the lower explosive limits of
methane, meaning that the methane concentration was dense enough to ignite
(Department of Employment, Economic Development and Innovation, 2010).
Compared to conventional gas which requires only a few well
heads CSG is extracted from many small reservoirs and requires a large number of
well heads of different sizes which dramatically increases potential for
fugitive emissions (Grudnoff, 2012).
The hundreds of kilometres of pipeline used to transport CSG
also offer many opportunities for fugitive emissions.
Combined with increases in emissions from wells during and
after fraccing this suggests that CSG emissions are far higher than conventional
gas but still lower than shale gas and only marginally lower than efficient coal
burning technologies (Grudnoff, 2012).
National and international accounting for global warming
potential (GWP) of CSG operations have mostly used the 100 year horizon which
places methane’s GWP as 25 times more than CO2 (Rutovitz et al, 2011).
But when the 20 year horizon was used methane’s global warming
potential was nearly 3 times higher at 72 times (Hardistry et al, 2012).
It may seem optimistic to use a 100 year horizon when so much
scientific evidence indicates that the next two decades will be crucial for
climate change direction.
Research indicates that a warming of 1.8 degrees Celsius above
the 1890-1910 base line will trigger a mass melting of permafrost in the arctic
constituting a rapid release of methane into the atmosphere from decomposition
of the peaty soils.
It is expected this melting will set in motion a positive
feedback loop for global warming caused by trapping of more heat from greenhouse
gases and reduction in surface albedo creating more heat absorption and
increased melting (Anisimov, 2007).
It is crucial to include in assessments that CH4 dominates the
global greenhouse footprint in the short term particularly when climate
mitigation strategies over the next ten to twenty years are considered the most
influential on economic and social futures (Howarth et al, 2012).